# Length units

🏆Practice length units

Units of length allow us to quantify length, height and distance.

Units of length to know.

A centimeter is equivalent to $10$ millimeters.

A meter is equivalent to $100$ centimeters.

One kilometer is equal to $1000$ meters.

## Test yourself on length units!

Calculate the surface area of the box shown in the diagram.

Pay attention to the units of measure!

## Example of an exercise with units of length

How many centimeters are there in 1.56 meters?

Here the calculation is quite simple.
If one meter is equivalent to $100$ centimeters we should multiply it by $100$ to get the number of centimeters.
$1.56\cdot100=156$

That is, $1.56$ meters equals $156$ centimeters.

## Another exercise with units of length

Sometimes we will have to solve exercises in which we will have to convert a unit to a much smaller one. In this case we will make an intermediate calculation and go through a unit that is "in the middle".

For example, how many centimeters are there in 2 kilometers?

We know that one kilometer is equivalent to $1000$ meters.

Therefore, we will first convert kilometers to meters and then meters to centimeters.

$1 km = 1000$ meters

$2 km =$ meters?

We will multiply the $2$ km by $1000$:

$2\cdot1000=2000$

Therefore, $2$ km equals $2000$ meters.

Now we will make the conversion to centimeters.

$1 metro = 100 cm$.

$2000 metros =$ centimeters?

We will multiply the $2000$ m by $100$ and we get:

$2000\cdot100=200,000$

Therefore, $2$ km equals $200,000$ cm.

Another way is to multiply directly: knowing that to convert kilometers to meters you multiply by $1000$ and to convert meters to centimeters you multiply by $100$, we can multiply $1000\times100$, that is, multiply directly by $100,000$.

We recommend doing it step by step to avoid confusion :)

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## Review questions

What is the concept of length?

Length can be defined as the part that measures an object from one side to another, that is, the distance between one point to another, the unit in the International System (SI) is meters, that is, we can measure the length of an object usually in meters, but there are also units of equivalence to this unit, such as centimeters, millimeters, hectometers, decameters and kilometers.

What are the instruments for measuring length?

There are different instruments to measure the length of an object or in other words the dimension or distance from one point to another, some of the most common instruments are the following:

• Ruler
• Measuring tape
• Tape measure
• Square
• Caliper

What is a unit of length?

A unit of measure will be the one that we will use as a reference to measure and quantify an object, in the case of the unit of length is the meter by the International System of Units. The meter is the unit of reference most frequently used to measure the length of an object.

How many centimeters are $27.5$ meters?

For this exercise we must know that centimeters and meters are units of measurement that are multiples, i.e. in this case $1m=100\operatorname{cm}$

So if a meter has $100$ centimeters, then let's make a multiplication

$27.5\times100\operatorname{cm}=2750\operatorname{cm}$

Then $27.5m$ equals $2750\operatorname{cm}$

How many centimeters are equal to $36.8$ inches?

In this case we must keep in mind that $1\text{pulgada}=2.52\operatorname{cm}$, so for this exercise let's do a multiplication

$36.8\times2.52\operatorname{cm}=92.736\operatorname{cm}$

Therefore $36.8$ inches equals $92.736$ centimeters.

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## Ejemplos y ejercicios con soluciones de וnidades de longitud

### Exercise #1

Calculate the surface area of the box shown in the diagram.

Pay attention to the units of measure!